Breeding & Isolation Box
Keeps fry safe without a second tank.
It hangs inside the main tank, so the fry are in water that is already heated, already cycled and already the right chemistry. That is the whole advantage over a separate container.
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- Sits in the main tank, so no separate heater
- Slotted sides let water flow through
- Divider separates fry from the parent
- Vented lid stops jumpers escaping
- Suction cups mount it to the glass
Why you'll love it
Made for happy, healthy pets
Fry do not need their own tank
The usual advice is a second heated, cycled tank, which almost nobody has ready when a fish drops fry unexpectedly. A box hanging in the main tank borrows the water you already have.
Slots, not solid walls
A sealed tub goes stale and swings in temperature within hours. Slotted sides keep the box on the same water as the tank, so the parameters cannot drift away from the fish inside.
It is also the hospital
Half of what this gets used for is not breeding. Isolating a nipped or bloated fish where you can watch it, and dose it, without netting it out of the system.
Good fit if
- Livebearer fry that would otherwise be eaten
- Isolating an injured or bullied fish without a second tank
- Watching a fish closely for a few days
- Keeping shrimplets safe in a community setup
Look elsewhere if
- You need to treat a fish with medication, which needs its own tank
- You have a genuinely contagious disease to quarantine
- You want to raise fry to adult size in it
Why in-tank beats a separate container
A separate container needs its own heater, its own filter and its own cycle, and setting one up in a hurry usually means none of the three. Fry moved to a bucket of fresh water face a temperature change, no biological filtration and rising ammonia within a day, which is worse than the risk they were moved away from.
A box hanging in the main tank sidesteps all of it. Slots let the tank water pass through, so temperature, chemistry and filtration are shared with the display. Nothing has to be matched because nothing is different, and there is no acclimatisation needed going in or coming out.
Fry, and the divider
Livebearers eat their own young, often within minutes. The divider addresses this by letting a heavily pregnant female sit above while the fry drop through to the section below, which puts them out of reach immediately without you having to catch anything.
Remove the female as soon as she has finished. Leaving her confined for days is stressful and she will not deliver well under it, and the box is small. The fry can then stay for a week or two before they need more room, which is well before they outgrow it.
Slot size and airflow
Check the slot width against the size of your fry before trusting it. Very small fry from egg layers can pass through slots designed for livebearer fry, and the first you know is an empty box. If in doubt, line the inside with a fine mesh for the first week.
Water exchange depends on flow reaching the box, so hang it where there is gentle circulation rather than in a dead corner. In a still spot the water inside stagnates despite the slots, and a small air stone or positioning it nearer the filter outflow solves that without creating a current the fry cannot handle.
In the box
Everything you need
- Isolation box
- Divider
- Vented lid
- Suction cups
How it works
Simple, from basket to doorstep
- 1
Browse
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- 2
Order
Check out securely with card, PayPal or one-tap Apple Pay & Google Pay. Free delivery over £45.
- 3
Delivered
Fast, tracked dispatch straight to your door, and a happier pet before you know it.
The details
Specifications
- Size
- About 12.5 × 7 × 7 cm
- Material
- Clear PS plastic
- Mounting
- Suction cups to the glass
- Use
- Fry, shrimp, or isolating a sick fish
- Weight
- About 50 g
Good questions
Before you buy
The slots are sized to hold newborn livebearer fry. Very small egg-layer fry are another matter. For those, keep the divider in and watch the first day before you trust it.
Days, not weeks. It is a nursery and a hospital, not accommodation. Fry go back out as soon as they are too big to be eaten.
Not usually, since tank water moves through the slots. If you have a very still tank, park it near the filter outlet so there is some flow past it.
Very small fry from egg-laying species can pass through. Check the slot width against your fry, and line the box with fine mesh for the first week if you are unsure.
Days rather than weeks for an adult, since it is small and confinement is stressful. Fry can stay a week or two before they need more space.
Not if it hangs where there is gentle circulation. In a still corner the water inside stagnates despite the slots, and a small air stone or a better position fixes it.
Last reviewed 30 August 2026